The invention relates generally to mechanical cardiopulmonary resuscitation techniques and more particularly, is directed to an improved massager pad for a cardiopulmonary resuscitator.
External cardiac compression can be effectively employed for obtaining perfusion by causing forced pumping of blood from a temporarily stopped heart. This is achieved by constant cyclic external compression of the heart (systole) for a short time period followed by pressure release to allow heart expansion (diastole) for a short time period. To achieve proper heart compression by external force, the breastbone or sternum is forced toward the backbone of the patient while the patient's back is rigidly supported.
Although forced pumping of blood is essential for a patient whose heart has stopped, this is only part of the continuous treatment necessary since once the heart stops, breathing stops also. Hence, when external mechanical or manual cardiac compression is presently employed, simultaneous sustained cyclic mechanical or mouth-to-mouth ventilation is also important to cyclically inflate the lungs for oxygenization of the blood. According to currently accepted medical practice, the lungs are ventilated or inflated during the diastole period of the compression cycle. Other techniques have employed ventilation simultaneously with external cardiac compression to use the relatively high intrathoracic pressures thus generated to enhance perfusion and the pumping of blood. Whether carried out mechanically or manually, these techniques comprise what is commonly referred to as cardiopulmonary resuscitation or CPR.
Current standards for teaching and practicing manual cardiopulmonary resuscitation specifies that the pressure for external cardiac compression is to be applied to the patient's sternum, using the heel of one hand and that care must be exercised to avoid applying any direct force to the patient's ribs. The rationale for these standards are stated to be that this technique creates more effective cardiac compression with less applied force and less risk of rib fracture.
Since specifications have not been formulated for mechanically applied CPR, it has been logical to use the expressed standards for manual CPR as a guideline for the design of mechanical cardiopulmonary resuscitators. Thus, the massager pad for all such mechanical devices have been designed to simulate the "heel of the hand" in shape, texture, and resilience.
By study of the anatomical structure, it is known that depression of the patient's sternum toward the vertebral column, as required by current CPR techniques, requires deformation of the rib cage in the form of substantially uniform bending of each rib throughout its length, and a hinging type of motion at the costa chondral junctures between the ribs and the patient's sternum. If the compression force is isolated on the sternum, substantial tension and sheer stresses are created in the costa chrondral junctures separation of the costa chondral junctures as a result of external cardiac compression. While such a separation of the costa chrondral junctures is not a fatal or serious trauma, it is nevertheless an undesirable complication of manual or mechanical CPR techniques.
Another trauma commonly observed with current CPR techniques is bruising and abrasion of the external chest produced by the relatively large pressures required to achieve adequate sternal deflection and adequate cardiac output. In large adults, these pressures can be as high as 60 pounds per square inch with either manual or mechanical CPR techniques.